[sundog01]

I am installing a new Xantrex TrueCharge 2 battery charger this weekend and am trying to figure out the “DC fused disconnect”. The directions state “Install a DC circuit breaker or fused disconnect in each positive cable within 7 inches of each battery.” What will work for the disconnect?

I have two battery banks and want to go straight to the batteries from the charger on the positive side then back to the charger via the neg. bus bar on the negative side. The charger is capable of up to three banks.

Thanks in advance for your help.

 

[negrini]

A circuit braker on such instalation seems too much inconvenient location to operate, thus a waste of money. In these cases, most common a fuse on each positive cable going to your batt. Westmarine does sell "in line" fuses for high amperage (your manual should state the desireable amps for each).

 

[Waltthesalt]

I don't know it this will help but relatively recently I've been seeing fuses that fit over the battery terminal to meet these ABYC requirements. A bit pricey but a slick solution.

 

[mitiempo]

These are the kind I use - they accept 30 - 80 amp maxi fuses.
Brian

 

[BELLATRIX1965]

Battery Terminal Fuses

The ABYC regs require what amounts to a fuse for the battery itself, thus everything connected to the battery is fused. Check out Blue Sea Systems web site; search for PN 5191 - Terminal Fuse Block, 3/8" Mounting Hole, 1 Terminal Stud. You need the fuse block AND an appropriate fuse module to go with it - make sure it is heavy enough to handle the whole battery load!
Good luck!

 

[mitiempo]

bellatrix
It has to be 2 separate fuses. Xantrex calls for a fused disconnect between the charger and the battery. This is a dedicated wire from the charger. I agree the battery should be fused in any case (unless it is a start battery in which case ABYC says it is optional). That fuse should be less than the ampacity of the main feed cable and close to the battery(s) capacity in amp hours. It is designed to protect the main feed wires in the case of a short - ie loose battery due to rough conditions, etc that would cause the battery to short out. The fused disconnect on the other hand should be sized for the wire gauge used for the charger's output. This will vary by both distance and charger model being installed.
Brian

 

[osirissail]

The one battery that really needs a main fuse is the engine starting battery. I have witnessed two boat burn up when the starter solenoid stuck and the battery cable caught on fire. A average starter can suck over a thousand amps out of the battery for the initial rotation of the engine. Since this only lasts for a few seconds it is not a problem with wiring or the battery. But if the solenoid sticks then the very high amperage continues and the cable catches on fire. I use a 350 amp buss bar fuse on the battery feed to the engine starter for a 6-cylinder Perkins. It has not blown so far as the engine starts in a few seconds. Too short a time for any heat to build up in the cable and fuse.

 

[mitiempo]

I agree a fused start battery is a good idea - just stated that ABYC considers it optional.
Brian

 

[Maine Sail]

The ABYC regs require what amounts to a fuse for the battery itself, thus everything connected to the battery is fused. Check out Blue Sea Systems web site; search for PN 5191 - Terminal Fuse Block, 3/8" Mounting Hole, 1 Terminal Stud. You need the fuse block AND an appropriate fuse module to go with it - make sure it is heavy enough to handle the whole battery load!
Good luck!

ABYC requires a fuse within 7" a power source. A battery fuse of 250 or 300 amps will not protect a 12GA wire for a charger..

 

[osirissail]

Whoo there, a 12 ga wire for a charger? it must be a rather small charger - 20 amp output or less. The big battery fuses are to protect the large battery cables which in my case are 4/0 cables.
Fusing the DC output of the shorepower charger is rather unusual so I assume the manual in post #1 is talking about the main batteries having fused protection, not the battery charger.
- - My battery chargers feed my DC system at each battery cable connection to the main DC switch. Then I use battery combiners to bridge over to the other battery bank should I be operating the main battery selector switch in any position other than "both". Only if the battery charger voltage exceeds the threshold will it charge the opposite bank protecting the other bank from discharging in to a lower voltage bank.
- - Hot wiring anything directly to the batteries rather than the main DC distribution panel is a recipe for an electrical fire - - unless the item has a fuse or c/b rated for lesser of the items wire size or operating amperage. And the fuse or c/b must be at the "supply" end of the wire feeding the item. This means a clutter of C/B's or fuses at or near the batteries which are subject to corrosion from battery gases.
- - If the proper size battery cable is used to feed the main DC distribution panel there is not logical reason to "hot wire directly to the battery(s). For protection of "loads" hot-wiring disables the purpose of the main battery switch which is to quickly and with one action totally disconnect all loads from the batteries to stop an electrical fire.

 

[mitiempo]

Battery chargers are required to have a fuse in the output wire to the batteries - at least according to Xantrex. The previous models (truecharge 20 and 40) were according to the manual to have fuses of 25 and 50 amps accordingly. The current model uses the chart I posted to determine fuse size based on gauge of the output wire.
Brian

 

[pdqaltair]

Recomendations, perhaps specifications. Government authorities make regulations.

ABYC requires a fuse within 7" a power source. A battery fuse of 250 or 300 amps will not protect a 12GA wire for a charger..

Good recommendations.

NEC and Coast Guard Code are regulations. Many associations (API, SAE, ASME, NFPA) make recommendations. They are "regulation" when adopted as part of a regulation.

Unless I misunderstand.

 

[osirissail]

Well, the addition of the fuses to the power output leads of the Xantrex battery chargers is something new. It was never mentioned by Xantrex or other battery chargers 10 years ago when I bought mine. Checking the Charles Battery charger manual - I just purchased a Charles, they also have a notation that the power leads from the battery need to be fused within 7" of the batteries. There have been several major changes in the ABYC recommendations in the last few years and obviously this is one of them. A friend of mine back when I was selling, repairing and installing marine equipment, was a member of the ABYC advisory committee(or whatever it was called) and frequently submitted suggestions for improvements to the standards. After I worked on 3 boats that had electrical fires due to unfused battery cables, he submitted a recommendation for a change in that subject area. He did say it took years to get anything through as they have to get input from a lot of places and then the agreement from the major boat manufacturers before they could publish. So I suppose this area was finally updated, which is very good news as 10 boats burn due to electrical fires for every one sinking due to collision with underwater obstacles.
- - Xantrex - I also have one as my #2 battery charger has a history of blowing out the output transistors/diodes. I have been through 3 of the chargers in 10 years. One of the failures was due to excessive back-voltage getting to the chargers and exploding them. The addition of the fuses/c/b's might help reduce that problem for the company. But the Charles manual specifically states the fusing is an ABYC standard. And the placement of the fuses "within 7 inches" of the batteries means that the purpose is to protect the connecting wires from the chargers to the batteries from catching on fire due to dead short at the charger. This is both logical and a good change in the ABYC standards. All wiring needs to be fused or have a c/b rated for the max carrying capacity of the wire or the load item at the end of the wire whichever is lower. The fuse/c/b should be located at the junction were a higher amount of power is available (e.g.: at the battery end; at the main distribution panel end).
- - The best reference book for all things mechanical and electrical is Nigel Calder's trusted Mechanical and Electrical Manual. I hope the book has been updated to reflect these recent (meaning last 5 years or so) changes. Or there may be other books more up to date. One of the best things about Nigel's book is the charts for wire sizes versus carrying load and wire run lengths. He had tables for both 4% and 10% wire loss. In general the book explains everything very well.
- - Always learning something new . . .
* There is a new amendment out by ABYC. ABYC is the major boat standards organization and also allied with the European ISO standards organizations. Insurance companies always want compliance with ABYC standards or they will not pay off, so boat manufacturers are very involved in the process of implementing the standards if they want to sell boats. Anyway the new amendment address electrical leakages on boats. I will put up a new thread on the subject.

 

[mitiempo]

While Calder's books are excellent, here's a better faster way to get the proper wire size for a particular purpose. Just plug in the % of loss, run length, and amperage it will have to carry and it gives you the proper gauge.
Brian
AWG by wire length/amps calculator

 

[BELLATRIX1965]

Perhaps TWO (2) fuses????

This is both logical and a good change in the ABYC standards. All wiring needs to be fused or have a c/b rated for the max carrying capacity of the wire or the load item at the end of the wire whichever is lower. The fuse/c/b should be located at the junction were a higher amount of power is available (e.g.: at the battery end; at the main distribution panel end).

OK - this makes sense to a point - however the point of highest potential is at the CHARGER, not the battery - otherwise, it would never charge the batteries! Maybe a charger lead should have a fuse at both ends???

 

[osirissail]

OK - this makes sense to a point - however the point of highest potential is at the CHARGER, not the battery - otherwise, it would never charge the batteries! Maybe a charger lead should have a fuse at both ends???

- - The word "Potential" is used in electric circuits to mean "voltage". It is the "amperes" that cause the heating problem (in combination with volts to make watts.) It would be extremely rare and IMHO virtually impossible for a battery charger to output an over-voltage significant enough to affect the wire safety. You can run many Kilovolts down a hair thin wire so long as the amperes are kept extremely low. TV CRT's (old fashioned tube-TV's) had several kilo-volts delivered to them in rather small size wires.
- - For instance during the starting of your engine, up to a thousand amperes race down your starting cable at 10 to 12 volts. Only because the time factor is a few seconds or less does the cable not catch on fire. Fuses and C/B's are rated to blow/trip only after a preset amount of time. Excessive amps through a C/B start a heating process that will "trip" it when sufficient heat is generated. After tripping you have to wait for the element inside to cool before you can reset the C/B.
- - The real threat to your wires - reference a battery charger - is the shorting of a component in the battery charger that would allow excessive amperage to flow from the "well/big supply" held in the batteries through the wires to the battery charger causing the wires to heat up and catch fire.
- - There are internal fuses inside the battery charger that will blow if you attempt to "suck" more power out of the battery charger than it is rated to supply. This would happen if there was an internal short in a battery or a dead short at the output of the battery charger. These protections have been in place for a very long time. What wasn't done previously was protect the wires from the battery supply end as it was considered highly unlikely that something could cause a dead short up inside the battery charger.
- - All the connections used to be up inside a compartment of the battery charger - now they are external to the battery charger case and some stray piece of metal could physically fall across the gap between ground and hot terminals causing the dead short.

 

[BELLATRIX1965]

My bad!

OK - right after I hit "Post", it dawned on me that my observation was not too sharp - for two reasons:

1) Absolutely - it's the current! The old formula P = i x e came instantly to mind.
2) Most battery chargers have a fused output - so there already IS a fuse on the charger end of the output wire!

Sometimes typing before thinking. . . .